How do I keep my company's data safe?

Permissions are given through roles, not individuals: you define a few roles such as owner, manager and staff, decide for each role what it can see, add, edit and delete, then assign every employee to a role with their own sign-in. An Excel file cannot do this reliably, which is why you need a system with sign-in and a database.

Take a copy of the program's data regularly and keep it somewhere other than the computer itself: an external drive, a second disk or cloud storage. A simple rule is one copy every working day and a weekly copy kept outside the shop. Most important, test a restore at least once, because a backup you have never restored cannot be trusted when you need it.

Keep the data locally on the computer if the program runs on one machine and you want it to work with no internet, accepting that backups are your job. Choose the cloud if several computers or branches need to see the same records at the same moment, and you accept that work requires an internet connection and a sign-in. The deciding question is how many computers need the data.

Move your old data in four stages: clean the file first so it has one header row and one kind of data per column; make dates, numbers and phone numbers consistent; test the import on a small copy of the file; then import everything and compare the row count and totals with the original. Keep the original file untouched and never edit it.